Tropical Storm LEE

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TROPICAL STORM LEE DISCUSSION NUMBER 5
NWS NATIONAL HURRICANE CENTER MIAMI FL AL132011
400 PM CDT FRI SEP 02 2011
DATA FROM SATELLITES...SURFACE OBSERVATIONS...DOPPLER RADARS AND AN
AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT INDICATE TROPICAL STORM
LEE HAS BECOME A LITTLE BETTER ORGANIZED DESPITE THE SIGNIFICANT
WARMING OF CLOUD TOPS IN THE NORTHEAST QUADRANT OF THE CYCLONE.
BUOY AND OIL RIG REPORTS OF 39-42 KT...ALONG WITH RELIABLE RECON
SFMR WINDS OF 38-40 KT...JUSTIFY INCREASING THE INTENSITY TO 40 KT.
THE INITIAL MOTION IS A SLOW DRIFT TO THE NORTH-NORTHWEST AT 2 KT.
LEE REMAINS TRAPPED IN A HIGH AMPLITUDE BLOCKING PATTERN THAT IS
FORECAST TO REMAIN INTACT FOR THE NEXT 24-36 HOURS AS A DEEP
MID/UPPER-LEVEL TROUGH OFF THE SOUTHEAST U.S. COAST AMPLIFIES AND
DIGS SOUTHWARD. BY 48 HOURS...THE NARROW RIDGE TO THE WEST OF LEE
THAT EXTENDS FROM DEEP SOUTH TEXAS NORTHEASTWARD TO MISSOURI IS
FORECAST BY ALL OF THE MODELS TO SLOWLY ERODE...WHICH SHOULD ALLOW
THE CYCLONE TO GRADUALLY GAIN LATITUDE AND MOVE TOWARD LOUISIANA. A
WEAK SHORTWAVE TROUGH FORECAST TO MOVE EASTWARD ACROSS THE SOUTHERN
AND CENTRAL PLAINS BY 72 HOURS SHOULD INDUCE A FASTER...ALBEIT LESS
THAN 10 KT...FORWARD MOTION TO THE NORTHEAST. BY DAY 4 OR 5...A
WEAKENED LEE IS EXPECTED TO MERGE WITH A FRONTAL SYSTEM AND BECOME
EXTRATROPICAL OVER THE LOWER TENNESSEE VALLEY. UNFORTUNATELY...THE
SLOW FORWARD SPEED OF THE CYCLONE IS EXPECTED TO PRODUCE A HEAVY
RAINFALL SCENARIO OVER LOUISIANA AND POINTS NORTHEASTWARD. THE
FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY TRACK AND IS A
BLEND OF THE GFS... UKMET...AND ECMWF MODEL TRACKS.
WATER VAPOR IMAGERY INDICATES THAT LEE HAS BECOME ENTANGLED WITH A
SMALL UPPER-LEVEL LOW. ALTHOUGH THIS CONFIGURATION SOMETIMES LEADS
TO A RAPID SPIN UP OF THE LOW- AND MID-LEVEL VORTEX...VERY DRY
MID-LEVEL AIR ASSOCIATED WITH THE LOW SHOULD CONTINUE TO BE
ENTRAINED INTO THE SYSTEM. THIS UNFAVORABLE CONDITION IS EXPECTED
TO INHIBIT THE DEVELOPMENT OF DEEP CONVECTION IN THE WESTERN
SEMICIRCLE FOR THE NEXT 12-36 HOURS...DESPITE THE VERTICAL WIND
SHEAR DECREASING TO LESS THAN 10 KT AND THE CYCLONE BEING OVER VERY
WARM SSTS DURING THIS TIME. BY 48 HOURS...THE VERTICAL WIND SHEAR
IS EXPECTED TO INCREASE FROM THE SOUTHWEST AHEAD OF A MID- TO
UPPER-LEVEL TROUGH...WHICH SHOULD ACT TO CAP OFF THE STRENGTHENING
PROCESS AS LEE ALSO MOVES OVER LAND. THE OFFICIAL FORECAST CALLS
FOR ONLY MODEST STRENGTHENING UNTIL LANDFALL OCCURS...AND IS
SIMILAR TO THE NHC INTENSITY CONSENSUS MODEL...ICON...WITH THE
STATISTICAL MODELS ABOVE AND THE DYNAMICAL MODELS BELOW THE
OFFICIAL FORECAST.
FORECAST POSITIONS AND MAX WINDS
INIT 02/2100Z 27.5N 91.5W 40 KT 45 MPH
12H 03/0600Z 27.9N 91.7W 45 KT 50 MPH
24H 03/1800Z 28.5N 91.7W 50 KT 60 MPH
36H 04/0600Z 29.2N 91.5W 55 KT 65 MPH
48H 04/1800Z 29.7N 91.1W 55 KT 65 MPH...INLAND
72H 05/1800Z 30.1N 89.9W 50 KT 60 MPH...INLAND
96H 06/1800Z 31.5N 88.2W 40 KT 45 MPH...INLAND
120H 07/1800Z 33.6N 86.7W 20 KT 25 MPH...POST-TROP/EXTRATROP
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FORECASTER STEWART
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